Electronic or electrical devices usually operate with suitable energy sources connected thereto. Common energy sources may include electrical sockets in a power grid, photovoltaic cells, fuel cells and batteries.
Portable electric devices, especially wearable devices are usually powered by portable energy sources such as batteries. The batteries are provided with a limited cycling stability and therefore the portable electric devices may be powered up by these batteries for a limited period of time. These batteries are designed to work in a charge-and-discharge cycle, which are particularly not convenient for wearable electronic devices which may operate continuously.